Can burner design



R. F- BUSWELL CAN BURNER D Sept. 19, 1961 ESIGN 2 Sheets-Sheet 1 //J Filed April 1, 1960 INVENTOR RICHARD F BUSWEL L q/MM A T TORNEV Sept. 19, 1961 F. BUSWELL CAN BURNER DESIGN Filed April 1, 1960 2 Sheets-Sheet 2 F/G4 J6 f6 45 6J6 4 INVENTOR RICHARD E BUSWELL A TTORNEV United States Patent 3,000,182 CAN BURNER DESIGN Richard F. Boswell, Wethers'field, Conn., assignor to United Aircraft Corporation, East Hartford, 'Conn., a corporation of Delaware Filed Apr. 1, 1960, Ser. No. 19,408 4 Claims. (Cl. 6039.65)

This invention relates to can type burners for use in combustion chambers and more particularly to can type burners having centertubes.

The main function of a combustion chamber and the burner therein is to efliciently mix and burn fuel and air therein so as to produce heated, energy ladened gases of combustion for work performing purposes. To effect efficient combustion it is necessary to first effect efiicient mixing between fuel and primary air so that :a stoichiometric mixture is attained. After the primary mixture is burned, the remainder of the air, or secondary air, is mixed with hot gases from the primary zone to cool the gas to a level which the turbine can withstand. This mixing occurs due to the turbulence of the gases. While turbulence is desirable from a fuel-air mixing standpoint, it results from the pressure loss of the air in passing through the combustion chamber and burner and a consequent reduction in power plant elficiency.

-In the past, in an attempt to reduce burner length and minimize burner'volume, annular burners, as opposedto can burners, have been tried but experience has shown that an annular burner has the inherent disadvantage that its outer wall collapses under the load imparted thereto by the pressure drop across the wall. Accordingly, while annular burners would presumably reduce burner length and pressure loss, they are not acceptable for large burner installations due to the aforementioned collapsing problem.

It has been found that for a given amount of turbulence or pressure loss the length required to mix and burn the fuel and air is proportional to the distance between the walls of the burner. -It has also been found that for a given size burner, the length required decreases as the turbulence-or pressure loss increases. With this in mind and realizing the inherent disadvantage of an annular burner, it is applicants object to teach that for best burner performance in compromise with power plant performance that a can or a series of can burners be used each with an annular centertube.

It is an object of this invention to teach a combustion chamber having a plurality of can type burners positioned circumferentially thereabout and each having centertubes including an annular centertube concentric about the burner axis so as to maintain the distance between the walls of the burner and the centertubes minimum and hence reduce pressure loss and burner lengt while increasing power plant efiiciency.

It is an object of this invention to teach a can burner construction in which efliciently operating burners may be fabricated of any size for a given or constant length, in short, to vary burner geometry as burner size increases so that it is not necessary to increase the burner length.

It is a further object of this invention to reduce the dimensions between the walls of a burner and hence the turbulence and pressure drop thereacross including placing a plurality of can burners with annular centertube circumferentially about an annular combustion chamber.

It is a further object of this invention to teach a can burner construction in which for a given burner size, the burner length may be reduced roughly, in accordance with the following table:

Patented Sept. 19, 1961 ice Table I Relative Number of Burner Fuel Centertubes Length/Diameter Nozzles/Can None 1.0 l 1 Normal .60 6 l Annular .33 9 l Annular and 1 Normal .25 19 2 Annular .20 24 Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate an embodiment of the invention.

In FIG. l is an external showing of a modern aircraft engine broken away in part to show my invention. FIG. 2 is a view taken along line 22 of FIG. 1.

FIG. 3 is an enlarged showing of the burner can illustrated in FIG. 1 to show a can-type burner using a single annular centertube.

FIG. 4 is a cross-sectional showing of a can-type burner using a normal centertube together with an annular centertube.

FIG. 5 is a cross-sectional showing of a can-type burner using two concentric, annular centertubes.

While I have chosen to illustrate a few embodiments of my can-type burner using annular centertubes, it will be obvious to one skilled in the art that there are several additional combinations available, however, there is a practical limit to the reduction in the dimension between the can walls and centertube walls in that eventually the number of fuel nozzles increases to the point that their size must be reduced to an impractical, small size which easily clogs and a quenching efiect which takes place when the aforementioned walls are too close which causes both efiiciency and the combustion limits of the burner to deteriorate.-

Referring to FIG. 1 we see modern aircraft space vehicle or engine 10 which is of the type which effects motivation by the creation of thrust due to the discharge of exhaust gases to atmosphere. While a turbojet engine will be illustrated, it will be evident to those skilled in the art that my invention is applicable to other flight vehicles utilizing similar combustion principles.

Jet engine 10 comprises air inlet section 12, compressor section 14, burner section 16, turbine section 18, and exhaust outlet 20. Compressor section 14, burner section 16 and turbine section 13 are axially aligned along axis 22 and enveloped within engine case 24. Engine 10 may be of the type taught in US. Patents Nos. 2,711,631' and 2,747,367.

In operation, air enters engine 10 through inlet 12, is compressed in passing through combustion section '14, has heat added thereto due to the combustion which takes place as it' passes through burner section '16, has energy to drive compressor 14 extracted therefrom in passing through-turbine section 18 and is. thence discharged to atmosphere through exhaust outlet 20 to.geI 1-, erate thrust.

Burner section 16 comprises annular combustion chamber 26 which is concentric about axis 22 and is defined by outer wall 28 and inner wall 30. A plurality of cantype or shaped burners 32 are positioned circumferentially about annular cavity 26 each being concentric about its own axis 34, which is radially offset from engine and combustion chamber axis 22.

As best shown in FIG. 3, can-type burner 32 basically comprises outer shell 36 which is cylindrical and concentric about axis 34 and annular centertube 38 which comprises outer and inner cylindrical walls 40 and 42 which are radially spaced from one another and concentric with respect to axis 34. It will be noted that walls 40 and 42 diverge at their forward ends 44 and 46 to smoothly blend with the forward end 48 of shell 36 and, further, smoothly converge at their after ends 56 and 52 to join and form centertube after end 54. It will be noted that cylindrical shell; 36 and walls 40 and 42 are all radially spaced with respectNto and concentric about axis .34.. Cylindrical shell 36 and walls 40 and 42 include a. plurality of axially spaced, primary holes such as 56 and 59 through which the air from compressor section 14 which is passing combustion chamber 26 'may pass as primary air into the enclosed combustion zone 58 formed by shell 36 and annular centertube 38., Cooling louvers 56 and 59 also extend through shell 36 and walls 40 and 42 for cooling-purposes due to the fiOW j of air therethroughi The after end of shell 36 reduces in cross-sectional area to define an outlet 60 through which. the heated gases of combustion created in combustion zone 58 pass before entering turbine section. 18; Secondary airports or apertures 62 through which secondary air from compressor 14 may pass into the interior of shell 36 downstream of combustion chamber 58 which mixes with and cools the very hot gas from the primary combustion to the desired, outlet temperature.

Fuel nozzles of well known construction 64, for example as shown in US. Patent No. 2,800,768, are positioned in the forward. end 48 of shell 36 and receives pressurized fuel from manifold 66 and fuel lines 68 so as to inject atomized fuel into combustion chamber 58 for mixing and burning with the primary air passing thereinto through primary holes 56' and 59'.

Referring to FIG. 4 we see can-type burner 32 of the same jet construction as previously described with respect to the FIG. 3 construction but including a normal, centrally located and substantially cylindrical centertube 70 and annular centertube 38' positioned concentrically radially outward thereof.

In the FIG. 5 construction we see can-type burner 32 used in conjunction 'with a first annular centertube 38' and a second annular centertube 38", each of which is of the type construction previously described for centertube 38 of FIG. 3 and concentrically envelops burner axis 34. I

It is to be understood that the invention is not limited to the specific embodiment herein illustrated and'described but may be used in other ways without departure from its spirit as defined by the following claims.

I claim:

1. In a combustion chamber having an axis, a can 2. In a combustion chamber having an axis, a can burner comprising a shell of circular cross section and having an axis parallel to and olfset from said combustion chamber axis and further having a forward end and a gas passage defining after end with an outlet, at least one annular centertube concentric about said shell axis and extending from and smoothly blending with said shell forward end toward said shell after end but terminating short thereof, fuel nozzles in said shell forward end, access holes in said 'shell and centertube through which air fromsaid'combustion chamber may enter, said shell and said centertube cooperating to define an enclosed combustion zonein which fuel from said nozzles may be burned with air from said access holes for eventual discharge as heated gases of combustion through said outlet. 7

3. In a combustion chamber having an axis, a can burner comprising a shell of circular cross section and having an axis parallel to and offset from said combustion chamber axis and further having a forward end and a gas passage defining after end with an outlet, centertubes smoothly blending with and projecting rearwardly from said shell forward end and including an annular centertube concentric about said shell axis and extending from said shell forward end toward said shell after end but terminating short thereof, fuel nozzles in said shell forward end access holes in said shell and centertubes through which air from said combustion chamber may enter, said shell and said centertube cooperating to define an enclosed combustion zone in which fuel from a; said nozzlm may be burned with air from said access from said shell forward end toward said shell after end burner comprising a shell of circular cross section and having an axis parallel to said combustion chamber axis and further having a forward end and a gas passage defining after end with an outlet, an annular centertube concentric about said shell axis and extending from said shell forward end toward said shell after end but terminating short thereof, fuel nozzles in said shell forward end, access holes in said shell and centertube through which air from said combustion chamber may enter, said shell and said centertube cooperatingto define an enclosed combustion zone in which fuel from said nozzles may be burned with air from said access holes for eventual discharge as heated gases of combustion through said outlet.

but terminating short thereofl'said annular centertube comprising outer and'inner cylindrical walls concentric aboutand: spaced radially with respect to said shell axis and. with said outer and inner walls diverging at their forward. ends to smoothly blend with said shell forward end and converging to smoothly join at their after ends forward of said outlet, fuel nozzles in said shell forward end, access holes in said shell and centertube through which air from said combustion chamber may enter, said shell and said centertube cooperating to define an enclosed combustion zone in which fuel fromsaid nozzles may be burned with air from said access holes for eventual discharge-as heated gases of combustion through said outlet.

References Cited in the file of this patent UNITED STATES PATENTS 2,609,663 Newcomb Sept. 9, 1952 2,828,609 Ogilvie l Apr. 1, 1958 FOREIGN PATENTS 670,092 Great Britain Apr. 16, 1952 

